the biggest thing with the 360 is compression, for most of the 360's life, they were low compression smog engines. So there's 2 area's i'd focus on. First, heads, being on a budget, I dont know what those flow like,
@IQ52 will know better but they're 75/76 360 heads with 1.88/1.60 valves. Get with IQ as he is a master when it comes to this.
Second, compression, only way to do this is with new pistons or decking the block, not sure what octane fuels are in Sweden, but stay under 10:1.
Any idea what rear gear you're gonna be running?